What keyword density actually is

When I talk about keyword density percentages I need to do so with care because it is not exactly what many claim. If my page has 100 words on it and I use 'sausages' once and 'bangers' once then my keyword density for sausages is 2%, not 1%, because 'sausages' and 'bangers' mean the same thing to a search engine designed to index UK English websites.

This is because search engines use Latent Semantic Indexing to understand the context of the page. Here they look for words similar to 'sausages' like (for the UK) 'bangers' and words that might be associated with 'sausages' such as 'skin', 'grill', 'spices', etc. That's why this page you are reading now might mention 'sausages' alot but it won't rank for that word! It is not in the overall context of the page or the website.

How search engines use keyword density

A search engine will look at the contents of a website to try and ascertain what it is about.
If it sees the word 'sausages' appear to a density of between 2 and 6% it is one factor it used to conclude that the page is probably about sausages but they'll need more convincing such as:

Is the word 'sausages' in the title and heading tags?

Is the word 'sausages' in the alt tags of any of the pictures?

Once you go over 6% (some people say 4%) the robot crawling the page is going to start suspecting you are scamming - you are trying to fool them into thinking this is the most important page ever about sausages because it gets mentioned so many times.
But a search engine robot won't conclude this. Instead it may discount the entire page, perhaps the website, as a scam.

You cannot use the same word, or even similar words, that often without losing readability.

The most common offender for scamming is overuse of the alt tag with an image. This isn't seen by users unless they have the graphics turned off on their browser so some website builders treat it as the ideal place to cram in keywords.
They'll create a tag like:

and so on. That's of no benefit to users and a recipe (excuse the pun) for being penalised by the search engines for scamming.

How some sites get away with keyword stuffing

Sometimes there really is no way to reduce the keyword density. A website that sells roses, for example, might mention the word 'rose' far too much and end up being treated with scamming suspicion.

But remember search engines also watch user behaviour.
If users - on a regular basis - go to that rose website, stay on it, click around, add it to their favourites or even create a link from their website to it then the search engine has to conclude,
"OK, I thought this website was scamming but user behaviour says it is above board - so no penalty here."

As with many SEO factors search engines must strike a balance between what their automated systems are programmed to spot and understanding the value of a page to internet users themselves.

Is keyword density fact or fiction?

I've talked a great deal about keyword density but you may have heard others claim that there is nothing in it ... this is just a myth.

Unfortunately search engines like Google won't give away the absolute truth but Google does talk about it. Here are a couple of videos on the subject:

However one thing many SEO professionals have got right is that you probably have other things to be worrying about when it comes to ranking and your time is better spent there. If your content is easy to read that is far more important than hitting some exact keyword density percentage because it is the positive user behaviour that will benefit you in the long run.

On the flip side people who try to keyword stuff end up with unreadable text or messy pages that send visitors to the door and rankings through the floor so there is no long term benefit there anyway.

In this sense keyword density actually takes care of itself and you are better off concentrating on creating great readable content and ensuring your keywords are in places that matter (see below).

The best way to handle keyword density

Keywords (or words that mean the same as the keyword) should be:

In the title tag of the page

In the meta description - yes, still use it!

In the first line(s) of the content and then spread throughout the text

In the alt tags of relevant images

Give your page a check to measure your keyword density (including words which mean the same) is not too low for your chosen keywords and phrases. If your text is easy to read you can virtually guarantee it will not be too high!

If you are on the low side edit carefully. Do not try and just put in a line like "sausage, sausages, sausage pictures" ... that is asking for trouble and is old school keyword stuffing in the extreme.

What to do about category and list pages

One type of page where keyword density often goes through the roof is lists, especially lists of products. If you have a list of pillowcases on your site the word 'pillowcase' may appear far too often for comfort.

There is no issue here as long as you make it clear to search engines that this is a list, not content. To do this: